Stress‐Drop Variations and Source‐Scaling Relations of Moderate Earthquakes of the Indian Tectonic Plate

Abstract

We investigate the source characteristics of 53 earthquakes in and around the Indian subcontinent through a grid‐search technique applied to the P ‐ and S ‐wave displacement spectra of regional waveforms registered at 42 broadband seismic stations. In addition, we estimate the P ‐ and S ‐wave attenuation factors representative of the various tectonic regions that constitute the Indian shield. We discuss the sensitivity of the displacement spectrum to various parameters and demonstrate that for a Brune‐type source model, the seismic moment is the best estimated parameter compared to others, such as the corner frequency. Our estimates of moment magnitudes are within the range of 1014–1020 (N·m), with the crack radii being less than ∼12 km. The nonuniform distribution of the static stress drop along the Himalaya, Burmese arc, and the western Indian regions indicates that the central Himalayas are prone to frequent failures owing to the lesser stress drop, in contrast with the northwestern Himalaya and Burmese arc regions. Our results suggest that median stress drops are independent of the earthquake mechanism. Online Material: List of events and associated estimated parameters.